Here's what you can do.
With one tank, buy at least 2 five gallon buckets and a battery powered air pump w air stone. Multiply that by the number of tanks if you have more than one.
Once you're ready to move...
1) Siphon some of the fish water into the two buckets. For smaller tanks, you'll probably need to add some declorinated tap water.
2) Put the decorations and plants in one of the buckets.
3) Net the fish into the second bucket. Maybe put some floating plants in with them.
4) Siphon most of the rest of the water out until you only have about an inch or two above the gravel. You can siphon it off to fill the two buckets, then put the remaining in another container to discard or take with you.
5) Rinse off the filter media in some of the leftover siphoned tank water, then put it in the plant bucket (or a bucket of its own). You need to keep it wet to preserve the bacteria colony.
6) Put the air stone in the fish tank and turn on the battery operated air pump.
7) Put the lids on the buckets and you're good to go.
I haven't found one yet, but it might not be a bad idea to find a battery powered heater (if it exists) to keep the fish warm enough. If you find one, let me and the rest of the message board know.